test: add ERT coverage for modeline-config and hugo-config

Add 67 tests across 6 new test files for modeline and hugo modules.
Refactor hugo-config: extract post-file-path and post-template helpers
from interactive new-post function for testability. Update todo.org
with test audit (31 modules), priority adjustments, and task cleanup.

1 files changed, 105 insertions, 0 deletions

diff --git a/tests/test-hugo-config-open-blog-dir-external.el b/tests/test-hugo-config-open-blog-dir-external.el
new file mode 100644
index 00000000..ae4a25ba
--- /dev/null
+++ b/tests/test-hugo-config-open-blog-dir-external.el
@@ -0,0 +1,105 @@
+;;; test-hugo-config-open-blog-dir-external.el --- Tests for cj/hugo-open-blog-dir-external -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the cj/hugo-open-blog-dir-external function from hugo-config.el
+;;
+;; This function opens the blog source directory in the system file manager,
+;; selecting the command based on platform:
+;; - macOS: "open"
+;; - Windows: "explorer.exe"
+;; - Linux/other: "xdg-open"
+;;
+;; We mock the platform detection functions and start-process to verify
+;; the correct command is dispatched per platform.
+
+;;; Code:
+
+(require 'ert)
+
+;; Add modules directory to load path
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+;; Stub dependencies before loading the module
+(unless (boundp 'website-dir)
+  (defvar website-dir "/tmp/test-website/"))
+(unless (fboundp 'env-macos-p)
+  (defun env-macos-p () nil))
+(unless (fboundp 'env-windows-p)
+  (defun env-windows-p () nil))
+
+(require 'hugo-config)
+
+;;; Test Helpers
+
+(defvar test-hugo--captured-process-cmd nil
+  "Captures the command passed to start-process during tests.")
+
+(defmacro with-platform (macos-p windows-p &rest body)
+  "Execute BODY with mocked platform detection.
+MACOS-P and WINDOWS-P control env-macos-p and env-windows-p return values.
+Mocks start-process to capture the command and file-directory-p to avoid
+filesystem checks."
+  (declare (indent 2))
+  `(let ((test-hugo--captured-process-cmd nil))
+     (cl-letf (((symbol-function 'env-macos-p) (lambda () ,macos-p))
+               ((symbol-function 'env-windows-p) (lambda () ,windows-p))
+               ((symbol-function 'file-directory-p) (lambda (_d) t))
+               ((symbol-function 'start-process)
+                (lambda (_name _buf cmd &rest _args)
+                  (setq test-hugo--captured-process-cmd cmd))))
+       ,@body)))
+
+;;; Normal Cases
+
+(ert-deftest test-hugo-config-open-blog-dir-external-normal-linux ()
+  "Should use xdg-open on Linux."
+  (with-platform nil nil
+    (cj/hugo-open-blog-dir-external)
+    (should (string= test-hugo--captured-process-cmd "xdg-open"))))
+
+(ert-deftest test-hugo-config-open-blog-dir-external-normal-macos ()
+  "Should use open on macOS."
+  (with-platform t nil
+    (cj/hugo-open-blog-dir-external)
+    (should (string= test-hugo--captured-process-cmd "open"))))
+
+(ert-deftest test-hugo-config-open-blog-dir-external-normal-windows ()
+  "Should use explorer.exe on Windows."
+  (with-platform nil t
+    (cj/hugo-open-blog-dir-external)
+    (should (string= test-hugo--captured-process-cmd "explorer.exe"))))
+
+;;; Boundary Cases
+
+(ert-deftest test-hugo-config-open-blog-dir-external-boundary-macos-takes-precedence ()
+  "When both macos and windows return true, macOS should take precedence."
+  (with-platform t t
+    (cj/hugo-open-blog-dir-external)
+    (should (string= test-hugo--captured-process-cmd "open"))))
+
+(ert-deftest test-hugo-config-open-blog-dir-external-boundary-creates-missing-dir ()
+  "Should create the directory if it doesn't exist."
+  (let ((mkdir-called nil))
+    (cl-letf (((symbol-function 'env-macos-p) (lambda () nil))
+              ((symbol-function 'env-windows-p) (lambda () nil))
+              ((symbol-function 'file-directory-p) (lambda (_d) nil))
+              ((symbol-function 'make-directory)
+               (lambda (_dir &rest _args) (setq mkdir-called t)))
+              ((symbol-function 'start-process) #'ignore))
+      (cj/hugo-open-blog-dir-external)
+      (should mkdir-called))))
+
+(ert-deftest test-hugo-config-open-blog-dir-external-boundary-skips-mkdir-when-exists ()
+  "Should not call make-directory if directory already exists."
+  (let ((mkdir-called nil))
+    (cl-letf (((symbol-function 'env-macos-p) (lambda () nil))
+              ((symbol-function 'env-windows-p) (lambda () nil))
+              ((symbol-function 'file-directory-p) (lambda (_d) t))
+              ((symbol-function 'make-directory)
+               (lambda (_dir &rest _args) (setq mkdir-called t)))
+              ((symbol-function 'start-process) #'ignore))
+      (cj/hugo-open-blog-dir-external)
+      (should-not mkdir-called))))
+
+(provide 'test-hugo-config-open-blog-dir-external)
+;;; test-hugo-config-open-blog-dir-external.el ends here